Excel's numerical precision is 15 decimal digits.
For identifiers, like credit card numbers, use text.
Two ways (at least):
a. Format the cell as text before entering the "number"
b. Precede the entry with an apostrophe; it will not show, but force the entry to be text

Signature
Kind regards,
Niek Otten
Microsoft MVP - Excel
| 15 max ?
|
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| > > Thank you for any help you can offer. PLease respond to
| > > d.wegner@komets.k12.mn.us